Heat exchangers



y 19, 1966 R. D. BAKER ETAL 3,

HEAT EXCHANGERS Filed Nov. 24, 1964 5 Sheets-Sheet l INVENTORS ROLAND D. BAKER AND JOHN W. BISHOP ATTORNEY July 19, 1966 R. D. BAKER ETAL HEAT EXCHANGERS 5 Sheets-Sheet 2 Filed Nov. 24, 1964 INVENTORS ROLAND D. BAKER AND JOHN W. BISHOP BY Q w OO MVOOOOOOO \DDOQDOOQ/ ATTORNEY July 19, 1966 R. D. BAKER ETAL 3,261,327

HEAT EXCHANGERS Filed Nov. 24, 1964 5 Sheets-Sheet 5 I i I i INVENTORS ROLAND D. BAKER AND JOHN W. BISHOP ATTORNEY United States Patent 3,261,327 HEAT EXCHANGERS Roland D. Baker, Alexandria, Va., and John W. Bishop, 92% Andover Drive, Alexandria, Va.; said Baker assignor to said Bishop Filed Nov. 24, 1964, Ser. No. 413,554 7 Claims. (Cl. 122-32) This invention relates to heat exchangers employing means for vaporizing liquids with a high pressure and temperature heating medium or gas in such a manner as to extend two passes of the heating medium or gas through a convection bank or unit disposed within and spaced from the walls of an outer steel shell or casing, to thereby dispense with the use of conventional boiler casing constructions normally made of sufficient strength as to withstand the temperatures and pressures of the heating medium employed. More particularly, the invention deals in a heat exchanger, wherein the convection bank or unit comprises spaced drums joined by inner bafiie walls and outer walls, between which and said drums the first and second passes of the heating medium extend and, further, wherein a multiplicity of liquid circulating tubes uniting the spaced drums are disposed in each of said passes.

Still more particularly, the invention deals with a heat exchanger of the character defined, wherein a controlled bypass is provided between the heating medium in one end portion of the casing of the exchanger and the exhaust or discharge of the heating medium from the other end portion of said casing and, further, wherein means is employed for discharging solids from the lower drum of said convection bank or unit.

The novel features of the invention will be best understood from the following description, when taken together with the accompanying drawing, in which certain embodiments of the invention are disclosed and, in which, the separate parts are designated by suitable reference characters in each of the views and, in which:

FIG. 1 is a diagrammatic sectional view of the heat exchanger illustrating the various intakes and exhausts therefrom and showing, in part, tubes extending between drums of a convection bank or unit, omitting showing of the other tubes to simplify the illustration and with parts of the construction broken away.

FIG. 2 is a diagrammatic sectional plan view of the structure shown in FIG. 1 illustrating the first and second passes of the heating medium and the bafile and outer walls of the convection bank or unit and,

1 further, illustrating, in part, the tubes in the respective passes.

FIG. 3 is a cross-sectional View, generally on the line 3-3 of FIG. 1, illustrating the upper and lower drums in elevation, with parts of the construction broken away and omitting background showing; and

FIG. 4 is a schematic view illustrating operation of a system in which the heat exchanger is arranged.

In carrying our invention into effect, we provide a simplified construction which eliminates the need of employing in the exchanger an outer shell or casing of the usual heavy construction or the need to insulate and/0r cool this shell or casing.

In illustrating one adaptation and use of the invention and, in considering FIG. 4 of the drawing, here is schematically shown at a heat exchanger. 11 represents a source of supply of a heating medium under high pressure which is directed to the exchanger 10 through a suitable pipe or passage 12. At 13 is shown a liquid separator forming the course of supply to the exchanger 10 through a feed pipe, diagrammatically shown at 14 in FIG. 4, and an exhaust or discharge pipe 15 for return of the liquid to 13. At 16 is diagrammatically "ice illustrated the steam exhaust from 13 and at 17 is the source of liquid supply to the separator 13. At 18 is diagrammatically illustrated the exhaust or discharge of the heating medium from the exchanger 10. At 19 is illustrated a bypass exhaust or discharge communicating with 18, 19 having a manually operated control, as indicated at 20.

Considering FIGS. 1, 2 and 3 of the drawing, 21 illustrates the convection bank or unit of the heat exchanger, this unit being supported within the shell or casing 22 intermediate ends 23 and 24 of the casing. At this time, it is pointed out that the showings in the several views are all brief diagrammatic showings, Without any of the structural details that normally would be employed. For example, the ends 23, 24 of the casing 22 may be head ends and at least the end 23 would be a head end to facilitate insertion of the unit 21 into the casing. It is also pointed out that the various couplings between the parts, which will be later described, will be welded or otherwise secured together, particularly in the various components of the unit and their association with the pipe 12 or its inner flared end 12' and the attachment thereof with the upper and lower drums 25 and 26 of the unit 21, together with the coupling of the pipe 14 with 26 and the pipe 15 with 25, as diagrammatically illustrated in FIG. 1 of the drawing. The pipe 12, together with the inner flared end 12' thereof, has an inner facing of high temperature resistant material, as diagrammatically illustrated at 27.

The drums 25 and 26 are joined by a pair of spaced bafile walls 28, note FIGS. 2 and 3, and other outer walls 29. Both pairs of walls are generally of the crosssectional contour shown in FIG. 3 of the drawing and these walls form, within the unit 12 and in combination with the drums 25 and 26, a first pass chamber 30, between the walls 28, and second pass chambers 31, between the walls 28 and 29 and at opposed sides of the chamber 30. The walls 29 will have a limited number of fine discharge apertures 32 to equalize pressure between the chambers 31 and the annular chamber in the casing 22 around the walls 29, as indicated at 33 in FIG. 2 of the drawing. The walls 28 and 29 are preferably formed of suitable high pressure and temperature resistant materials and this is also true of the structure of the shell or casing 22, including the ends 23 and 24 thereof. Arranged within the chamber 30 are a multiplicity of liquid transmitting tubes, diagrammatically seen, in part, at 34 in FIG. 2 and arranged in the chambers 31 are similar tubes 35. The tubes 34 and 35 are arranged generally at right angles to the drums 25 and 26.

Considering FIG. 3 of the drawing, it will appear that end portions of the tubes are fixed to the drums 25 and 26 and, for the most part, are tangentially arranged with respect to the drums. The coupling between parts of the tubes 34 with the drums 25 and 26 is illustrated in the broken away sectional portion, as at 34' in FIG. 1 of the drawing.

Considering FIG. 2 of the drawing, it will appear that the chamber 30 opens into the chamber 36 in the end 24 of the casing 22, as seen at 37, so that the heating medium can extend into the open ends 38 of the chambers 31, as diagrammatically illustrated by the arrows 39. The heating medium, after passing through the chambers 31, is discharged through open ends 40 of the chambers 31 into the chamber 41 of the head end 23 of the casing 22 for discharge from the chamber 41 through the discharge pipe or duct18.

It will be apparent from a consideration of FIGS. 1 and 2 that the bypass 19 communicates with the chamber 36, so that, as and when required or desired, part of the heating medium in the chamber 36 can be bypassed into 18 through operation of the control, as diagrammatically seen at 20. In this manner, the temperature of the discharge from the pipe or duct 18 can be controlled and regulated.

Considering FIG. 1 of the drawing, it will appear that a discharge pipe 42 is coupled with the lower drum 26 and extends through the casing 22 for discharge of suspended solids in the liquid in what is termed a bottom blow down and this discharge can include a control, as diagrammatically seen at 43.

The feed of liquid to the bottom drum 26 is preferably a gravity feed and the steam and liquid vapors extending to the drum 25 will be discharged through the pip and returned to the separator 13, as schematically illustrated in FIG. 4 of the drawing.

With our improved system, it will be apparent that the high temperature and pressure medium introduced into the first pass defined by the chamber 30 prevents this high temperature and pressure from coming into direct contact with th Wall structure of the casing 22, including the ends thereof. This temperature medium, at a lower temperature, which would prevail in the chamber 36, then will extend through the second pass, defined by the chambers 31 and be discharged into the chamber 41 at a still lower temperature, from which it passes out through the pipe or duct 18. In this connection, it will be apparent that operation of the bypass 19 will provide a close control of the heating medium discharge or exit temperature by mixing with the normal discharge or exhaust into 18 a part of the higher temperature of the heating medium which prevails in the chamber 36. From a consideration of FIG. 2 of the drawing, it will be noted that the walls 29 include an annular baffle 29' which prevents the heating medium in the chamber 36 from passing directly into the annular chamber 33 at the end 24 of the casing 22.

By providing the first and second passes in a convection bank or unit as defined, very high temperatures can be employed in the heating medium without danger of direct contact with the shell or casing of the exchanger. In other words, this high temperature is materially reduced before it has opportunity to contact any of the wall structure of the casing.

By providing a convection unit including the drums as a complete assemblage, this assemblage can be fabricated at any source of supply and then arranged within or assembled in a shell or casing. This arrangement would also provide means for making repairs to the unit when removed from the shell or casing. With these characteristics in mind, a more simplified and economical heat exchanger structure is provided.

Having fully described our invention, what we claim as new and desire to secure by Letters Patent is:

1. In a heat exchanger, a pressure containment casing, a convection unit mounted within and spaced from the walls of said casing, said unit having upper and lower drums, said unit having a pair of inner baffle Walls coupled with said drums in defining a first inner pass and a pair of outer walls coupled with said drums in defining, in com bination with said inner walls, a second outer pass, tubes crossing both passes and coupled with said drums, means at one end of the casing admitting a heating medium to flow through said first inner pass and then through said second outer pass in delivering heat to vaporize a liquid in said tubes, said unit having means confining the heating medium to said passes throughout the major part of the length of said casing to thereby reduce temperature of the heating medium prior to said heating medium coming into contact with said casing, means at the other end of the casing placing the first pass in communication with the second pass, a discharge duct for said heating medium at the first 4. end of the casing, and bypass means at the second named end of the casing placing said last named means in communication with said discharge duct.

2. A heat exchanger as defined in claim 1, wherein said bypass means includes a control.

3. In a heat exchanger comprising a casing, a convection unit in said casing and spaced from the walls thereof, said unit comprising upper and lower drums, said unit having a pair of inner walls coupled with said drums in defining a first inner pass and a pair of outer walls coupled with said drums and defining, in combination with said inner walls, a second outer pass, a plurality of liquid transmitting tubes connecting the drums in each pass, means at one end of the casing admitting a heating medium from a source of supply to the first pass, said heating medium being directed to the second pass at the other end of said casing, said heating medium delivering heat to vaporize a liquid in the tubes of said convection unit, said unit controlling the temperature of the heating medium to reduce the same prior to coming into direct contact with said casing, a discharge duct for said heating medium at th first named end of the casing, and bypass means placing the second named end of the casing in communication with said discharge duct.

4. In a heat exchanger comprising a casing, a convection unit in the longitudinal, central portion of said casing and spaced from the walls thereof, said unit comprising upper and lower drums extending longitudinally of the casing, said unit having means defining, in combination with said drums, a first inner pass and means defining, in combination with said drums and said first named means, a second outer pass, a plurality of fluid transmitting tubes connecting the drums in each pass, means at one end of the casing admitting a heating medium from a source of supply to the first pass, means forming a chamber at the other end of the casing exposed to both passes, said heating medium being directed to the second pass through said chamber, said heating medium delivering heat to vaporize a liquid in the tubes of said convection unit, said unit controlling the temperature of the heating medium to reduce the same prior to coming into direct contact with said casing, a discharge duct for said heating medium at the first named end of the casing, and bypass means placing the second named end of the casing in communication with said discharge duct.

5. A heat exchanger as defined in claim 4, wherein the lower drum includes a blowdown discharge.

6. A heat exchanger as defined in claim 4, wherein said third named means comprises an insulated pipe disposed in the first named end of the casing and directed solely to said first pass.

7. A heat exchanger as defined in claim 4, wherein means is provided for gravity feed of the liquid to the lower drum and the tube of said convection unit, and said upper drum having an exhaust directed to said last named means.

References Cited by the Examiner UNITED STATES PATENTS 2,980,081 4/ 1961 Bennett 1227 3,118,431 l/l964 Banker et al 122--333 FOREIGN PATENTS 983,444 4/ 1948 France.

KENNETH W. SPRAGUE, Primary Examiner. 

1. IN A HEAT EXCHANGER, A PRESSURE CONTAINMENT CASING, A CONVECTION UNIT MOUNTED WITHIN AND SPACED FROM THE WALLS OF SAID CASING, SAID UNIT HAVING UPPER AND LOWER DRUMS, SAID UNIT HAVING A PAIR OF INNER BAFFLE WALLS COUPLED WITH SAID DRUMS IN DEFINING A FIRST INNER PASS AND A PAIR OF OUTER WALLS COUPLED WITH SAID DRUMS IN DEFINING, IN COMBINATION WITH SAID INNER WALLS, A SECOND OUTER PASS, TUBES CROSS BOTH PASSES AND COUPLED WITH SAID DRUMS, MEANS AT ONE END OF THE CASING ADMITTING A HEATING MEDIUM TO FLOW THROUGH SAID FIRST INNER PASS AND THEN THROUGH SAID SECOND OUTER PASS IN DELIVERING HEAT TO VAPORIZE A LIQUID IN SAID TUBES, SAID UNIT HAVING MEANS CONFINING THE HEATING MEDIUM TO SAID PASSES THROUGHOUT THE MAJOR PART OF THE LENGTH OF SAID CASING TO THEREBY REDUCE TEMPERATURE OF THE HEATING MEDIUM PRIOR TO SAID HEATING MEDIUM COMING INTO CONTACT WITH SAID CASING, MEANS AT THE OTHER END OF THE CASING PLACING THE FIRST PASS IN COMMUNICATION WITH THE SECOND PASS, A DISCHARGE DUCT FOR SAID HEATING MEDIUM AT THE FIRST END OF THE CASING, AND BYPASS MEANS AT THE SECOND NAMED END OF THE CASING PLACING SAID LAST NAMED MEANS IN COMMUNICATION WITH SAID DISCHARGE DUCT. 